No, tossing the keys on the counter and going "Do the HEI upgrade" is not going to happen. That's why there's a detailed article I linked you to, going step-by-step on how it's done, what parts you need, etc.
Pretty much
nothing on your '73 Valiant is common knowledge any more. Most of the knowledge that used to be common about these cars can no longer be found (in heads or in books) at most shops, which are equipped and staffed and trained for the last 25 years' cars. You will have to either do your own work, find a specialty shop, or bring in literature (and sometimes even parts) to let a regular shop try their hand at it. This is the kind of thing that goes with driving an old car.
You'll want to start by getting the three books described in As soon as you can, get the three books listed in
this thread as quickly as you can.
